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WWUS20 KWNS 180201

SEL9

SPC WW 180201

IAZ000-ILZ000-180800-



URGENT - IMMEDIATE BROADCAST REQUESTED

SEVERE THUNDERSTORM WATCH NUMBER 339

NWS STORM PREDICTION CENTER NORMAN OK

900 PM CDT THU JUN 17 2010



THE NWS STORM PREDICTION CENTER HAS ISSUED A

SEVERE THUNDERSTORM WATCH FOR PORTIONS OF



       CENTRAL AND EASTERN IOWA

       NORTHWEST ILLINOIS



EFFECTIVE THIS THURSDAY NIGHT AND FRIDAY MORNING FROM 900 PM

UNTIL 300 AM CDT.



HAIL TO 2.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80

MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.



THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 90

STATUTE MILES EAST AND WEST OF A LINE FROM 70 MILES SOUTH

SOUTHWEST OF DES MOINES IOWA TO 25 MILES NORTH NORTHEAST OF

WATERLOO IOWA.  FOR A COMPLETE DEPICTION OF THE WATCH SEE THE

ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU9).



REMEMBER...A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE

FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH

AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR

THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS

AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY

DO PRODUCE TORNADOES.



OTHER WATCH INFORMATION...CONTINUE...WW 333...WW 334...WW

335...WW 336...WW 337...WW 338...



DISCUSSION...BROKEN LINE OF INTENSE THUNDERSTORMS IS TAKING FORM

AHEAD OF A SLOW MOVING COLD FRONT FROM NRN TO SWRN IA ATTM. LIFT

AHEAD OF THE FRONT WILL CONTINUE TO SPAWN STORMS IN A VERY UNSTABLE

AIRMASS. STRONG SHEAR ACROSS THE REGION SHOULD FURTHER SUPPORT STORM

ORGANIZATION WITH LINE SEGMENTS AND POSSIBLE SUPERCELLS PRODUCING

DAMAGING WINDS AND LARGE HAIL.



AVIATION...A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT

TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 70

KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 600. MEAN STORM

MOTION VECTOR 27025.





...CARBIN

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